Transcript Circulation - Salisbury Composite High School

Circulation
The human circulatory system
consists of 96,000 km of blood
vessels that transport blood to
each cell in the body. Your
entire blood volume (about 5L)
is pumped every minute.
The circulatory system performs the
following functions:
1. carries oxygen and nutrients to the cells
2. carries carbon dioxide and waste away from
the cells
3. carries hormones to target organs
4. distributes heat throughout the body
5. helps defense of invading micro-organisms
Blood Vessels
Arteries – carry blood away
from the heart. Their thick walls
are composed of three distinct,
elastic layers. Each time the
heart pumps, the arteries
stretch to accommodate the
rush of blood. This is felt in the
neck, or on the wrist as a pulse.
Arterioles - are smaller arteries
whose middle layer is
composed of elastic fibers and
smooth muscle. The arterioles
are able to contract and relax,
controlling blood flow to different
parts of the body.
Vasoconstriction –
the narrowing of
blood vessels,
decreasing flow to
the tissues.
Vasodilation – the
widening /
relaxation of blood
vessels, increasing
flow to the tissues.
Capillaries – are tiny blood
vessels composed of a
single layer of cells. This is
the site of fluid and gas
exchange between the
cells and the body
tissues. Many capillaries
are only as thick in diameter
as one red blood cell
(<0.005 mm). Pressure in
the capillaries is high,
increasing the risk of
rupturing and causing a
bruise.
Venules – larger blood vessels that form as
capillaries merge. The venules are lined with
smooth muscle to ensure blood continues to
flow back towards the heart.
Veins – larger blood vessels that result as
venules merge, take blood back towards the
heart. Veins also serve as blood reservoirs,
holding up to 65% of the total blood volume.
Blood pressure in the veins is quite low, so the
veins have uni-directional valves that ensure the
one way flow of blood. Skeletal muscles also
help aid venous flow. Venous pressure
increases when skeletal muscles contract and
push on the vein, forcing blood upwards.
Blood Vessels
Problems with blood vessels:
Aneurysm – a bulge or
weakening in the wall of a
blood vessel.
Atherosclerosis –
degeneration of blood
vessels caused by the
accumulation of fat
deposits (plaque) in the
inner wall.
Bruising – rupture of
capillary beds cause
blood to leak into the
extra-cellular space.
Varicose Veins –
damage to the oneway valves in veins
causes blood to pool
and the veins to
bulge.
Circulation
The heart consists of two parallel pumps. The right
connects to blood vessels that circulate blood to the
lungs, for oxygenation, and back to the heart. This
system is called the pulmonary circulatory
system. The second, left hand pump, connects
blood vessels to the body and circulates blood to
the body tissues. This system is called the
systemic circulatory system.
One way blood flow is maintained by unidirectional valves in the heart and in the blood
vessels.
Pulmonary
System
Systemic
System
Heart Anatomy
Atria - top chamber of the heart that contracts to
push blood into the bottom ventricular chamber.
Aorta – largest artery in the body, carries
oxygenated blood to the body tissues.
Atrioventricular (AV) valves – the tricuspid
(Right side) and bicuspid valves (left) separate
the atria from the ventricles on the right and left
sides respectively. These valves ensure a one
way flow of blood within the heart. Chordae
tenidea anchor the valves to ensure one way
flow.
Coronary arteries – branch from the aorta and
supply the heart muscle with oxygenated blood.
Pulmonary arteries / veins – carry
deoxygenated blood to (artery) and oxygenated
blood from (vein) the lungs.
Semi-lunar valve – prevents blood from flowing
backwards from the pulmonary artery / vein,
back to the ventricles.
Septum – muscular wall that separates the left
and right sides of the heart.
Vena Cava – largest vein that carries blood from
the upper body (superior) or lower body (inferior)
back to the heart.
Ventricles – large muscular chambers that
pump blood to the lungs (right), or to the body
(left). The wall of the left ventricle is thicker
because it pumps blood further to the body
tissues.
Blood Flow Through The Heart
Blood always flows in one
direction through the heart:
Body cells (deoxygenated
Inferior / Superior Vena Cava
Right Atrium
Right Ventricle
Pulmonary Artery (to lungs)
Pulmonary Vein (from lungs)
Left Atrium
Left Ventricle
Aorta
HeartCenterOnline:
Blood Flow Through Your Heart
and Lungs
Setting the Heart Beat
The heart muscle is unique because it is myogenic
muscle. That is, it is able to contract without external
nerve stimulation. The heart beat is controlled by the
sympathetic (stimulating) and parasympathetic
(relaxing) branches of the nervous system. The heart’s
rate or tempo is set by a small mass of tissue in the right
atrium called the sinoatrial (SA) node. This is known as
the muscles pacemaker. Contractions radiate from the
SA node and travel to the atrioventricular node (AV)
node through the bundle of His, which passes nerve
impulses along two large nerve fibers called Purkinje
fibers to the septum and the ventricles. The resulting
wave of contraction moves from the atria to the
ventricles, up from the bottom of the ventricles, forcing
blood out the atria / pulmonary arteries.
http://www.msjensen.gen.umn.edu/1135/Links/Animation
s/Flash/0028-swf_the_cardiac_cy.swf
Normal Heart Rate – 80
beats/minute
Bradycardia - < 50 beats/min
Tachycardia - > 100 beats/min
Systole – contraction of the
heart muscle
Diastole – relaxation of the
heart muscle
Electrical Signals and Blood
Flow
ECG
ElectroCardioGram
Shows the electrical conductivity of the heart
and is used to identify and diagnose heart
conditions.
Heart Institute: Heartbeat Animation
Heart Sounds and Cardiac Cycle
The familiar lubb-dubb sound of the
heartbeat is caused by the closing of the
heart valves.
Time (s)
Atria
Ventricle Sound
Valves
0.15
Systole
Diastole
Lubb
AV closed
0.30
Diastole
Systole
Dubb
Semi-Lunar
closed
0.40
Diastole
Diastole
0.85
Both Closed
Heart Murmur (lubb-dubb-squish)– occurs
when the heart valves are faulty and don’t
close completely. Blood rushes from the
ventricle back into the atrium creating a
squishing sound that is heard as a murmur.
Transport: Cardiovascular System - Heart
Sounds
Cardiac Output and Blood Pressure
Cardiac Output – is the amount of blood that
flows out of the heart each minute. Output can
be influenced by stroke volume and heart rate.
Stroke volume – is the volume of blood pumped
with each beat of the heart. On average, the
stroke volume is about 70 ml/beat.
Heart rate – is the number of beats per minute
of the heart.
Cardiac Output = Stroke volume x Heart rate
Example:
If Tom has a stroke volume
of 85 mL and a heart rate of
100 beats per minute, what
is his cardiac output? If the
dog has a stroke volume of
50 ml and a heart rate of
120 beats per minute, what
is his cardiac output?
Tom: 85 mL/beat x 100
beats/min = 8500mL/min.
Dog: 50 mL/beat x 120
beats/min = 6000 mL/min.
Blood Pressure – is the force of
the blood on the walls of your
arteries. Blood pressure is
measured with a stethoscope and
a sphygmomanometer (or blood
pressure cuff). Normal blood
pressure is 120/80. That means
that the systolic pressure (during
contraction) is 120 mm Hg and the
diastolic pressure (during
relaxation) is 80 mm Hg. Blood
pressure is influenced by age,
level of fitness, level of hydration
and level of stress.
Blood pressure depends on two major factors:
BP is measured by baroreceptors (stretch
receptors) in your aortic arc or the carotid artery
– 1. Cardiac output (blood volume and Heart Rate) – higher blood
volume = higher pressure, this may also be influenced by fluid
retention (such as water). Higher heart rate = higher BP
– 2. Arteriolar resistance (blood vessel size)– the diameter of the
arteries will determine the pressure within them. Vasoconstriction
will cause greater BP. Vasodilatation decreases BP
Ex. High BP will be interpreted by the baroreceptors and signal the
medulla omblongta to do 2 things to drop the BP to normal:
– 1) decrease the sympathetic nervous system cause vasodilatation
– 2) increase the parasympathetic nervous system  slow the heart rate and
decrease the blood volume
Measuring Blood Pressure
A sphygmomanometer
(blood pressure cuff)
measures blood
pressure:
Systolic / Diastolic
pressure is on average
120/80 mm Hg.
Blood Pressure Center HeartCenterOnline:
Capillary Fluid Exchange
Nearly every tissue of the body is within 0.1 mm of a
capillary. The capillaries carry valuable oxygen, glucose
and amino acids to cells, as well as remove wastes like
carbon dioxide.
Extra-cellular Fluid (ECF) – fluid that occupies the
spaces between cells. This fluid will then come into
contact with both cells and the capillaries to facilitate the
transport of oxygen, glucose, amino acid and waste.
Fluid Pressure/Filtration: BP created by the heart and
blood volume filter oxygen and nutrients out of the
capillaries at the arteriole end
Osmotic Pressure/Absorption: Pressure created by
water pushed CO2 and waste back into the capillaries at
the venule end
Arteriole End
-A high BP on the inside of the vessel
vs. a low osmotic pressure on the
outside of the vessel allows for
oxygen and nutrients to be squished
outwards and into the
ECF to be picked up my cells
Venule End
-A low BP on the inside of the vessel
vs. a high osmotic pressure on the
outside of the vessel allows for
CO2 and waste to be squished
inwards and into the
blood vessel to be delivered back to
the heart
Exchange of nutrients, wastes and gases
occurs by two forces:
Fluid Pressure / Filtration – blood pressure in
the vessels due to ventricular contraction forces
materials such as water, small minerals and ions
out of the blood, and into the ECF.
Osmotic Pressure / Absorption – large
proteins and dissolved minerals in the blood
create an osmotic gradient that draws fluid into
the capillaries.
– Osmotic Pressure - Learning Activity
The Lymphatic System
Lymph – a fluid found outside the capillaries
that contains some proteins that have leaked
through the capillary walls.
Lymphocytes – white blood cells that produce
antibodies to help fight infection.
Lymph nodes – are masses of tissue that store
lymphocytes that fight infections and remove
foreign particles from the body.
Lacteals – collect fatty acids and glycerol form
the villi in the small intestine and take them to
the blood.
Lymph Nodes - Animation - - UMMC
To ensure that lymphocytes and lymph fluid is
evenly distributed throughout the body, a
network of open-ended canals called lymph
vessels create the lymphatic system. The
lymphatic system has three basic functions:
Absorb excess issue fluid and proteins and
redirect them back to the blood.
Absorb digested fats from the small intestine.
Fight infection and remove foreign materials
from the blood.